Temperature control system



Oct. 5, 1943. GRQQMS. I 2,331,025

TEMPERATURE CONTROL SYSTEM Filed June 27, 1941- 0 INVENTOR WMVfi/ Patented Oct. 5, 1943 TEMPERATURE CONTROL SYSTEM Albert 0. Grooms, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application June 27, 1941, Serial No. 400,124

3 Claims.

sures therein according to temperatures so that it will operate as a temperature control.

It is another object of my invention to provide a temperature control requiring no bellows or diaphragm but having a rang and/or difierential adjustment.

To attain these objects I have provided an electron tube of the cold cathode type and provided it with a. grid. The interior of the tube is connected'to a thermostat bulb which controls the vapor pressure within the tube according to the temperature so as to control the flow of electrons in the tube. In one form several sets of electrodes may be provided in the tube with selective connections outside the tube so that the temperature at which the electron flow starts and stops may be readily ontrolled by this means. Also, a rheostat is connected to the grid so as to independently control the temperature at which the electron-flow stops. The tube may be used to control an electrical device such as a relay which may be used to control the other devices or a motor or similar device may be connected directly in the tube circuit.

Further objects and advantages of the present invention will be apparent from the following description, referenc being had to the accompanying drawing, wherein a preferred form of the present invention is clearly shown.

In the drawing:

Fig. 1 is a view of a refrigerator embodying one form of my invention; s

Fig. 2 shows a wiring diagram illustrating the control operating through the medium of a relay;

Fig. 3 is a view showing the tube connected directly in series with the motor driving the re-' frigerating system; and

Fig. 4 shows a modified form in which the tube contains a plurality of electrodes provided with selective external connections.

Referring now to the drawing and more particularly to Fig. 1, there is shown a refrigerator containing a food compartment 22 cooled by a refrigerator evaporator 24 under the control of a suitable temperature control. One form of such a control is shown in Fig. 3 in which the refrigerating system is illustrated diagrammatically and includes a compressor 26 for withdrawing evaporated refrigerant from the evaporator 24 for forwarding the compressed refrigerant to the condenser 28 where it is liquefied and is returned to the evaporator under the control of a suitable liquid control device 30. The compressor 26 is driven by an electric motor 32 which may be either of the single phas induction type or a commutator type.

This motor 32 is connected in series with the supply conductor 34 and in turn is connected by the conductor 35 to the plate electrod 38 within the electron tube 40 which is provided with a sealed envelope of glass or metal, or some other suitable material. The tube 40 is provided with a second plate electrode 42 which is connected directly to the other supply conductor 44. The tube 40 is also provided with a grid 46 located between the plates and connected by the conductor 48 to the variable resistance 50 provided with a variable contact device 52 operated by an adjustment knob 54. Connected to the variable resistance 50 is a conductor 55 which is connected either through the switch 58 directly to the supply conductor34 or through a suitable capacitor 50. The interior of the sealed tub 40 is connected by the tube 62 to a thermostat bulb 64 which is clamped in heat exchange relation to the evaporator 24. The tube 40, th tubing 62 and the thermostat bulb 64 are charged with some suitable vapor such as a mercury vapor or bromine vapor.

I find that with these vapors there is a range of pressures at which the electrons will flow from one of the plates to the other and allow the electric motor 32 to drive the refrigerating system. When the temperature and vapor pressure is increased above this range the flow will cease and likewise when the temperature and vapor pressure is reduced below this range the flow will cease. I propose to operate at the lower end of the range and to make the distance between the plates 38 and 42 such that when the evaporator temperature rises to a point showing the need for operation ofthe system, electrons will flow from between the plates 42 and 38 and cause operation of the motor 32 to drive the refrigerating system. When the evaporator. is cooled sumciently the flow of electrons will stop due to the lowering of the vapor pressure within the tube 40 under control of the thermostat bulb 64.

In order to provide a manual means for varying the temperature and pressure at which the electron-flow stops the variable resistance 50 is used. Since the motor 32 has considerable induction, the current flowing by means of the electrons between the plates lags out of phase ing the capacitor 60 to supply the leading current to-the grid. This provides two difierent methods for controlling the stoppage of electron-flow through the grid circuit.

Fig.'2 shows a diagrammatic circuit in which a relay 94 is connected in series with the supply conductors I34 and I 34 instead of the motor 32. The relay 94 controls the operation of an electric motor I32 for controlling the operation of the refrigerating system or other device. The tube I46 is illustrated diagrammatically and is provided with a thermostat bulb I64. The remainder of the circuit is similar to that shown in Fig. 3.

In Fig. 4 the tube 2% is provided with a grid 2 36 and plate electrodes 238, 239, 242 and 2 33. A selector switch 210 connects either of the electrodes 238 or 239 to the electrical device 232 which in turn is connected to the supply conductor 23%. A selector switch 212 connects either of the electrodes 2132 or 253 to the supply co'nductor 244. By suitably operating the selector switches 210 and 272 four diiferent electrode arrangements may be used. Naturally when the electrodes used are closer together the starting and stopping bulb temperatures and the corresponding vapor pressures will be lower and when the electrodes used are further apart the starting and stopping bulb temperatures will be higher. The tube 2%0 may likewise be connected'to a thermostat bulb 214. However, the bulb is merely a convenient means for causing the vapor within the tube to respond to the temperature of the element, such as the evaporator, to be measured. If desired the tube may be placed directly in heat exchange relation with the temperature to be measured or which serves as the source of control. It will be seen that this control is comparatively simple and avoids the use of bellows and diaphragms.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might'be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A temperature control for controlling an electric device comprising an electron discharge device including an envelope containing a tem perature responsive ionizable material and three electrodes located at various distances from each other, each of said electrodes being insulated from the other, an electric device to be controlled, and selective means for connecting the electric device selectively in series with any two of said electrodes and disconnecting the other electrodes from the electric device.

2. A temperature control for controlling an electric device comprising an electron discharge device including an envelope containing a temperature responsive ionizable material and three electrodes located at various distances from each other, each of said electrodes being insulated from the other, an electric device to be controlled, and selective means for connecting the electric device selectively in series with any two of said electrodes and disconnecting the other electrodes from said device, a grid within said envelope, and means for varying the flow of current to the grid.

3. A temperature control for controlling an electric device comprising an electron discharge device including an envelope containing a temperature responsive ionizable material, a first set of electrodes located a certain distance apart, a second set of electrodes located a greater distance apart, said electrodes all being insulated from each other, an electric device to be controlled, and selective means for disconnecting either set of electrodes from said electric device and for connecting the other set to said device.

ALBERT O. GROOMS. 

